Isomerization



I'EICIIICU aan. l, nH-l ISOMERIZATION Winfield Scott, deceased, late of Akron, Ohio, by Ruth P. Scott, executrix, Akron, Ohio, assignor to Wingfoot Corporation, Akron, Ohio, a corporation of Delaware No Drawing. Application August 9, 1943, Serial No. 497,972

6 Claims. 1 This invention relates to the isomerization of alpha-beta unsaturated acids and esters from the cis to the trans form. The invention lies in the use of a. conversion agent, without which no detectable conversion occurs. The invention includes the isomerization of such compounds in which one or more of the hydrogens connected directly to a carbon atom have been replaced by chlorine, alkyl or other substituent. The ester may be an alkyl ester, such as methyl, ethyl, propyl, etc., or an aralkyl ester, such as benzyl, etc. It includes the isomerization of angelic-acid esters to tiglic-acid esters; cinnamic esters from the cis to the trans isomer; chlormaleic-acid esters to chlorfumaric-acid esters; citraconicacid esters to mesaconic esters; crotonic-acid esters from the cis to the trans isomer; etc.

According to this invention, the isomerization is effected in the presence of an isomerizing agent which contains the grouping include the thiazoles, thiazolines, thiuram disulfides, etc., are:

2-mercaptobenzothiazole Benzothiazyl disulfide Z-mercaptothiazoline (l|J- S CHa-C 4J-SH 2-mercapto-4-methylthiazole C S H CHa-C -S-CH2OH Mcthylol-Z-mercaptoi-methylthiazole (CH3)2N. C (S) S20 (S) .N CH3) 2 Tetramethyl thiuram disulfide N C S N I ll k/ S H Piperidinium N,N-pentamethylene dithiocarbamic acid The invention will be illustrated by the following examples:

Ezramp le 1 A mixture of 15 grams of diethyl maleate and 0.3 gram of 2-mercapto-4-methylthiazole was heated in an oil bath at about 140 C. Every five minutes, a 0.4 ml. sample was withdrawn and mixed with 0.6 ml. of Nujol. The consolute temperature of this mixture was determined, and from it, the percentage of diethyl fumarate in the reaction mixture was calculated. The results are given below:

Example 2 A mixture of 5 grams of monomethylmaleate and 0.1 gram of Z-mercaptothiazoline was heated at about 140 C. for one hour. The mixture darkened considerably during this time, but on cooling, monomethyl fumarate crystallized out. Weight of product, 2.1 grams (42 per cent).

Example 3 Two and a half grams of 2-mercapto-4-methylthiazole were dissolved in grams of water, and 100 grams of maleic anhydride were added. The mixture was heated at its boiling point with stirring for about 2.5 hours. Upon cooling, the solution yielded grams of fumaric acid. Further heating for 4 hours and distilling ofi most of the water resulted in the separation of an additional 22 grams of fumaric acid. Total yield, 95 per cent.

Example 4 A mixture of 15 grams of diethyl maleate and Derivative converted Agent H Maleic acid 2. 109-101 89 D 2.0 109-101 77 4. 0 109-101 88 2. 5 109-101 76 Do 6. 5 109-101 95 Monomethyl maleate. 1.0 140 42 Dimcthyl maleate 2. 5 190 80 0. 5 160 75 1% iodine 1. 0 160 36 1% Z-mercaptobenzothrazole 1. 0 160 60 1% 2-mercapto-4-methylthiazole 1.0 160 93 1% methylol-2-mercapto-4-methylthiazolc 1.0 160 98 1% cyclohexylamine derivative of zinc thiofuroate. 0.5 160 16 1% tetramethyl thiuram disulfide 1.0 160 79 1% benzothiazyl disulfide 1.0 160 13 1% piperdinium pentamethylene dlthlocarbamlc acid 1.0 160 41 1% Z-mcrcaptoquinoline 1.0 160 (33 0.15 gram of 2-mercaptobenzothiazole was heated at about 160 C. for one hour. A determination of the consolute temperature revealed that 60 per cent of the maleic ester had been converted to the fumarate ester.

Example 5 A mixture of 5 grams of diethyl maleate and 0.025 gram (0.5 per cent) 2-mercapto-4-methylthiazole was heated at about 120 C. for 80 minutes. Thirty-two per cent of the ester was converted to the fumarate.

Example 6 ture resulting from the heating of the alpha beta 5 unsaturated acid or ester with any of the suitable isomerizing agents of this invention, is heated to about 120 C. (or some temperature higher than the consolute temperature of the mixture) and then the heated mixture is allowed to cool and the temperature at which the mixture just begins to become clouded is observed and is referred to as the consolute temperature. This temperature is referred to a chart (on which is plotted a series of consolute temperatures and corresponding conversion percentages obtained from known mixtures) and the corresponding percentage conversion obtained.

Other conversion agents include: Z-mercaptothiazole, thiazyl disulfide, 4-methylthiazyl disulfide, tetraethyl thiuram disulfide, tetra- =butyl thiuram disulfide, methYlol-Z-mercaptobenzothiazole, methylol-2-mercaptothiazole, dipentamethylene thiuram disulfide, diethyl ammonium diethyl dithiocarbamic acid, etc.

What is claimed is:

1. The process of isomerizing diethyl maleate to the diethyl fumarate which comprises the step of heating the maleate in the presence of 2-mercapto-4-methyl thiazole at a temperature of about C. until conversion is substantially complete.

2. The process of isomerizing dialkyl maleates which comprises heating the dialkyl maleate in the presence of tetramethyl thiuram disulfide.

3. The process of isomerizing dialkyl maleates which comprises heating the dialkyl maleate in the presence of Z-mercapto-4-methyl thiazole.

4. The process of isomerizing diethyl maleate which comprises heating the compound in the presence of z-mercaptol-methyl thiazole.

5. The process of isomerizing dialkyl maleate which comprises heating the dialkyl maleate in the presence of a catalyst from the group consisting of 2-mercaptobenzothiazole, 2-mercaptothiazoline, 2-mercapt0-4-methyl thiazole, methylol-Z-anercaptol-methyl-thiazole, tetramethylthiuram disulfide, Z-mercaptothiazole, thiazyl disulfide, 4-methyl thiazyl disulfide, tetraethyl thiuram disulfide, methylol-2-mercaptothiazole, dipenta methylene thiuram disulfide and diethyl ammonium diethyl dithio carbamic acid.

6. The process of isomerizing a dialkyl maleate which comprises heating the dialkyl maleate in the presence of 2 -mercaptobenzothiazole.

RUTH P. SCOTT, Emecutrz'a: of the Last Will and Testament of Winfield Scott, Deceased. 

